Wireless power supply methods such as an electromagnetic induction method, a radio wave receiving method, an electric field coupling method, and a magnetic field resonance method are known. Among these methods, the magnetic field resonance method relates to a technique in which each of the side of a power transmitting device and the side of a power receiving device includes an LC resonance circuit, which is made up of a coil and a capacitor, and a magnetic field between the two LC resonance circuits is resonated to wirelessly transmit electric power (see Japanese Unexamined Patent Application, First Publication No. 2011-147271 described below).
In comparison with the electromagnetic induction method that is widely put to practical use, the magnetic resonance method is possible to realize highly efficient and long-distance power transmission under a weak magnetic field, and is attracting attention as a next-generation wireless power transmission technique available for charging portable terminals, electric vehicles, and the like.